1. A new water service main to the house. PVC or CPVC, probably 1.25"
2. One long copper run through the house. Probably 1".
3. Add filters and regulators in the garage. Either 3/4" or 1" copper, depending on the size of those nice pair of 20" filters I picked up at the swap meet for $10. Eh lets say all 1" copper there.
4. Sprinkler systems in 2 locations, all 3/4" PVC

Everything indoors will be copper. Underground portions will be PVC or CPVC. I've got a few questions you guys might know something about....

My experience is that most PVC leaks occur at fittings. Specifically those damned elbows and T's crack a lot. Straight couplings and bushings seem to be ok. In locations I never want to dig up again, can I use brass elbows and T's on PVC? Or are Sch 80 fittings thick enough? Of course using a threaded brass T would mean gluing a threaded coupler onto the PVC first, and that itself could crack. But straight pieces like that don't seem to crack like the L's and T's. I'm way too busy to spend a weekend digging up another leak. I just want a lifetime solution. And I just married a hot Thai girl who will outlive me by 50 years. Which, by the way, I highly recommend for you single guys. So, is 75-100 years too much to ask in a water main?

For the copper runs, I've seen that thicker pipes are available. My feeling is Type K is probably overkill, and fantastically expensive. I'm sure Type L will be fine. Anyway I'm again more worried about the fittings. I've not seen any sort of ratings on copper fittings which indicate which are thicker or better. They all look rather thin to me. Are there better ones? I have a lot less experience with copper, so maybe fitting failures are less a problem. Is that the case?

Fortunately I have no major leaks at the moment, so I have the time to do my homework and plan it out. But there's one old galvanized sprinkler line seeping, which will only get worse, so no time to waste.

I've seen copper fittings fail before thicker pipe does before. That was on a swimming pool. Too much chorline I would think.
Though if the water is good, it should last a long time. In Washington, I use type L underground.
For underground plastic, I don't see anything wrong with PVC, though like you mention, the fittings are the weak link there.
I have noticed lately that some Male Adapters look to have stronger looking thread portions.